The process of fiting some statistical model to a particular set of data. Mostly done on a computer, and using varied numerical methods such as optimization or numerical integration, or simulation.

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4 views

Purpose of multiple models with fixed slope

I'm fairly ignorant when it comes to fitting models, and I'm having trouble grasping the point of fitting more than one line with the same slope. Is this generally used in a context with factors, ...
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20 views

Fitting an envelope to x-y data in R

I have some data that I'd like to create an envelope for it. As in the picture, the data is always positive and I'm looking for something that will capture my crudely hand drawn red line. It should ...
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16 views

min ChiSquare to fit dipole axis

I am trying to fit a dipole. As I am not sure about some aspects (and not sure whether I understand it at all) I would like to ask this question here. Basically I have a distribution of $n$ sample ...
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6 views

apply fitted model to data and obtain loglikelihood [migrated]

I would like to do the following in Python, preferably with the statsmodels package (but if you know a solution with another package, I would be glad to hear about it as well): I have data ...
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20 views

How to fit quantized data

I have some measurements which were quantized during measuring. Now I want to get the overall change during a period of time, e.g. 15 minutes. Because of quantization however, the same value is ...
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15 views

How to divide scattered points among multiple curves? [duplicate]

I have the following scattered points graph: To me, it seems that the points describe 2 (maybe 3) logarithmic curves. Is there a way to say which point belongs to which curve?
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1answer
45 views

Do predicted values differ if variables included stepwise or simultaneously?

You make a linear model #1 of the following form to predict adult human height: $$ y = \beta_{0.1} + \beta_{1.1}\text{Height}_\text{dad} + \beta_{2.1}\text{Height}_\text{mom} $$ You calculate fitted ...
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25 views

choosing between non-linear/logistic regression models

We are fitting regression models to dose-reponse data obtained from drug assays. Where a drug has an effect on cell viability, there is often a sigmoidal relationship between the proportion of viable ...
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8 views

Linear fit parameter-errors as a function of the number of data-points

I am trying to work out the errors of $m$ and $b$ in a linear least-square fit of a straight $y = m \cdot x + b$ to $N$ equally-spaced data points $Y_i$ on the interval $I = [-\Delta x \cdot ...
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23 views

How do I interpret which model is the best fit for my distribution (AIC)?

I'm new here so looking for some guidance; How do I interpret the following variables to understanding which model is considered the best fit to my distribution. ...
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12 views

Fit a transition matrix

Probably I am asking something very simple, but I am unable to figure out the answer from previous posts. I have a set of data with the age (in years) an the condition (in a class form 1 - good to 5 - ...
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1answer
89 views

Finding probability distribution that describes data

I have tried to fit several distributions to my continuous data (Pareto, Log-normal, Exponential, Gamma). The distribution of data is given below. I used Kolmogorov-Smirnov test to compare my data ...
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18 views

Should I still compare my distrbution to others if I've found a fit?

I'm using the ghpy package in R to model some currency data. I currently comparing fits with the lik.ratio.test with the ...
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3 views

How do I evaluate if an SIR model is consistent with a new-product diffusion model?

Background Susceptible-Infected-Recovered (SIR) models are used in epidemiology to determine the spread of disease. (link) The Bass models for new product diffusion are textbook in sales. (link) ...
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1answer
33 views

Beta distribution vs beta binomial distribution: alpha and beta

I have been attempting to estimate alpha and beta from a beta binomial distribution given my data. There are R packages like VGAM to do this. I am wondering if there is a difference between estimating ...
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2answers
62 views

How do you count the number of parameters in a time series model?

I am learning about time series analysis and want to perform Box-Ljung tests of the residuals of my fitted models, e.g. ...
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0answers
11 views

Does Prism use smoothing to calculate a non-linear fit to data?

I have some read out vs. concentration of an agonist. I calculated EC50 using Prism6. My method was pretty simple. Log transform concetrations. Fit the data using log(agonist) vs. response -- ...
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1answer
15 views

Is golden section search considered a fitting (regression analysis)?

I am curious if the Golden section search is a form of fitting (or regression analysis in general)? It does find the extremum, but independent of any functional form (it works without modeling, if I ...
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20 views

Why does Empirical Bayes work in my simple case?

I have a problem where I am trying to classify data into two groups using a single parameter. The distribution of this parameter is Gaussian for two groups, so what I'm dealing with is two overlapping ...
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39 views

What have I done wrong implementing this Bayesian method for fitting a circle to noisy data?

I have noisy measurements of movement along a circle. I want to fit a circle to these measurements. I tried two methods, a straight forward moment fit, and then an ODR fit (described here. However ...
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31 views

How can I fix a poor nonlinear curve fit?

I was trying calculating Fourier transform of some rings. as follow: By directly calculating of model as several rings, the result showed different from the the experimental ones. So I tried to ...
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1answer
53 views

Find distribution of underlying feature

Let's say I have a dataset with values for the variable $W$. The distribution of $W$ doesn't follow any obvious known distribution. I have a model that gives $W$ as a functions of $E$ and $K, W = ...
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2answers
68 views

Fitting a GEV distribution - non-negative only

I am fitting a GEV distribution to some rainfall data, but the software I am using (Matlab and Easyfit) are giving a distribution which includes negative numbers (i.e. negative rainfall). Is there a ...
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15 views

estimating model fit parameters using simulations

I'm trying to fit 2D ellipticals gaussians to an image (with correlated background noise) using prewritten fitting software. I'd like to know about the uncertainty in the fit parameters with this ...
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28 views

loglikelihood for HMM with continuous emissions

I have a HMM and that has continuous valued emissions. I model the emissions using Weibull distributions. After I run the HMM I get the states, transition probabilities, priors and shape,scale ...
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7 views

Fit vertices to minimize Error when linearly interpolating

For a curve like the one below: Given that we have a certain amount of vertices for approximation, say 5. How to find appropriate x values to place the vetices on ...
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30 views

Fitting multiple normal distributions to sample data

I have a data set of (time, action)-tuples. Actions are typically performed at approximately the same times every day, and depending on what the action is it may be done multiple times per day. If I ...
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1answer
105 views

Fitted Beta distribution always holds water. Can I force it not to?

I am trying to fit a beta distribution to election forecast data. The ultimate purpose is determining with what probability the election will be decided by one vote (more on this here). My data is as ...
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24 views

geeglm not recognizing clusters

I am fitting a geeglm model and it is not recognizing the clustering. my model is ...
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0answers
113 views

How to determine if GLM quadratic term should be set up orthogonal or non-orthogonal

I am setting up a GLM in R where I have only one predictor variable and its quadratic form. I understand that in R I have 2 options. ...
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36 views

Do we fit this time series data with time series model or spline?

Basically, I have the following data with the number of item A on the vertical axis and the time on the horizontal axis (from 1st hour to the 24th hour). I don't have much experience in fitting a ...
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77 views

Align two datasets in Python

I want to develop some python code to align datasets obtained by different instruments recording the same event. As an example, say I have two sets of measurements: ...
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53 views

How do I verify whether a population distribution is a power-law? [duplicate]

given a population of discrete values (not a sample), is there any way to check whether the distribution is a power-law, and with what parameters? Of course I can just plot the distribution and see ...
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28 views

Least-squares fitting with only optimum features, after Lasso - valid?

Using Lasso reduces the coefficients of features of a model, reducing some to zero, and thereby performing feature selection. The number of features depends on the value of $\alpha$ aka $\lambda$. In ...
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22 views

Least Squares Regression - Error [duplicate]

In standard least squares regression, we find constants $\beta_1$ and $\beta_2$ such that the square of the average error, $\epsilon = y_i - (\beta_1 + \beta_2x_i)$, is minimized, and so the 'line of ...
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50 views

How to run an nls model in R to generate output parameters for independent categories?

I would like to get help on the following code: library(nlme) funct1 <- function(scale1,a){ exp((scale1 - 2)/a) } ...
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1answer
37 views

How to calculate the probability of a datapoint fitting in a known distribution

I have a set of samples, each with a concentration for element A which is shown on a log scale on X-axis on the histogram below. The number of samples with the same concentration is shown on Y-axis. ...
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14 views

How to fit raw signal

I think this is simple, but somehow it's not working. I'm trying to fit my raw data so that basically I end up with beautiful 1 peak. I tried butterworth filtering, Gaussian fitting, a combination of ...
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24 views

How should I fit this data?

I have a dataset: ...
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2answers
183 views

Power law fitting of data with uncertainties

I need to fit data points on a power law and each one of these carries an uncertainty. I've been using Python, more precisely scipy.optimize.curve_fit to get the job done but I don't know how to ...
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1answer
25 views

Is there a statistical differing interpretation between match and fit?

I've seen the terms matching/match and fitting/fit used almost interchangeably when discussing models goodness of fit, observed vs simulated data matching, etc. Is there a difference in ...
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19 views

Limiting the range of possible values for distribution fitting with GAMLSS in R

I'm trying to fit ST5 distribution for reaction times with GAMLSS. Sometimes mu parameter of the distribution is negative, which is implausible. Is it possible to limit the range of parameter values ...
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1answer
48 views

Regressing, analysing data with points rather than polynomial?

I am looking into making a regression of a bunch of data that is contained on some range of real numbers. In my case, x is between 0 and 1 and y is between 0 and 10. If I have 150 data points on this ...
2
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0answers
31 views

Fitting a straight line to components of complex numbers

I have a strange problem that I'm not sure how to solve: I have complex data points in a time series. The amplitude of these complex numbers in the time series forms a straight line, which I have fit ...
2
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0answers
21 views

Polynomial Data Fitting for Two Unknown Equation

I have a kind of data and want to find the equation(poly coeff) of given data. For example equation for given sample data is simple a^2*b+10 ...
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1answer
56 views

code for ordered probit model

I have a data set with 7 predictor variables and one dependent variable. The dependent variable has 4 categories so it's not binomial. I need to fit a probit model. I need codes for probit model in ...
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1answer
26 views

Comparing polynomials

I've got a bunch of data on pop singers' performance on the Hot 100 charts over time, and I'm trying to compare the early part of different artists' careers. For example, I might look compare Miley ...
4
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1answer
353 views

Determining probability distribution for datasets with missing values

As a part of my exploratory data analysis (EDA) prior to further analysis, I'm trying to determine a probability distribution of my pilot dataset's variables. A particular feature of this dataset is a ...
7
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2answers
981 views

What to do when CFA fit for multi-item scale is bad?

I am not sure how to proceed with this CFA im doing in lavaan. I have a sample of 172 participants (I know that’s not much for a CFA) and 28 items with 7-point Likert scales that should load on seven ...
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1answer
430 views

Fit measures for GMM Arellano-Bond estimator in R

A colleague and I have been working with difference GMM, i.e. the Arellano-Bond estimator, in R. Our option has been to use the pgmm command from the plm package. However, now I am struggling to test ...